JP2008110512A - Mold for three-layer foam pipe and method for producing three-layer foam pipe using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a three-layer foamed tube which can produce a three-layer foamed tube in which a vinyl chloride-based resin composition is less likely to stay or decompose in a resin passage, has no uneven thickness or insufficient foaming of a foamed intermediate layer, and does not easily cause flat cracks. A mold for a layer foam pipe and a method for producing a three-layer foam pipe using the same.
A substantially cylindrical core, a cylindrical inner layer land / intermediate layer core, surrounding the core, and forming an annular first inner layer resin passage between the core and a portion of the core, the core and the inner layer A spider having a through hole installed in a land and an intermediate layer resin passage that surrounds the land and intermediate layer core and forms an annular intermediate layer resin passage between the core and the inner layer land and intermediate layer core The land is provided with a second inner layer resin passage that opens to the annular outer layer resin passage and the intermediate layer resin passage, and the second inner layer resin passage has a through hole of the spider. A mold for a three-layer foamed tube that communicates with the upstream side of the first inner-layer resin passage.
[Selection] Figure 1

Description

  The present invention relates to a mold for a three-layer foamed pipe and a method for producing a three-layer foamed pipe using the same, and more particularly to a method for producing a vinyl chloride resin three-layer foamed pipe.

  Synthetic resin resin pipes are widely used in pipelines and pipeline systems such as waterworks, sewage systems, and piping because they are easy to connect and bond and have corrosion resistance. In recent years, it has been desired to be lightweight while maintaining rigidity and impact fracture strength, and in order to achieve that purpose, a method of corrugating the tube wall, a tube with ribs, and a rigid thermoplastic resin for foaming Various methods have been proposed, such as a tube using a slab. In particular, a resin tube in which the inner layer and the outer layer are formed of a non-foamed thermoplastic resin layer and the intermediate layer is formed of a foamed thermoplastic resin layer has been attracting attention as a resin tube that can be reduced in weight while maintaining rigidity and impact resistance. Yes.

  In addition, in the case of resin products formed with vinyl chloride resin, etc., and when recycling the resin by recovering waste materials generated during manufacturing, one of the product forms manufactured using recycled resin, There is a resin tube having a three-layer structure in which the intermediate layer is formed of a foamed thermoplastic resin layer. Furthermore, in a three-layered resin tube, a recycled resin is generally used for the thermoplastic resin forming the foamed thermoplastic resin layer.

Various proposals have been made as molds for producing such a three-layer foamed tube. For example, as shown in FIG. 3, (a) an extruder body, (b) a mandrel 104 at the outer end, A cylindrical central body portion 113 extending rigidly from the extruder body; (c) surrounding the central body portion 113 and forming a first annular gap 107 between at least a portion of the central body portion 113; A concentric first cylinder 115 abutting and rigidly supported by the extruder body; (d) surrounding the first cylinder 115 and forming a second annular gap 106 between at least a portion of the first cylinder 115; One end surrounds the second cylinder 115 ′, which concentrically supports the one end of the first cylinder 115 in an interlocked state, and (e) the second cylinder 115 ′. An outer body portion 115 "having a cylindrical cavity forming a third annular gap 105 between at least a portion and (f) fixing the one end of the second cylinder 115 'and the first cylinder 115 and the second cylinder; Means 116 for rigidly supporting 115 ′ and outer body portion 115 ″ on outer body portion 115 ″ in an interlocked state with the extruder body in the above-described gap relationship; (g) first and third annular gaps 107; A first passage 109 for receiving molten material from a first source in communication with 105 and a second passage 112 for receiving molten material from a second source in communication with a second annular gap 106; Having a multilayer wall composite structure constituted by means for attaching a die 103 for forming into a wall pipe to the outer end of the outer body portion 115 "through a gap with the mandrel 104 An apparatus for extruding a plastic pipe (see, for example, Patent Document 1) has been proposed.
Japanese Patent Publication No. 7-51308

  However, when forming a three-layer foamed tube using the above-mentioned extrusion apparatus, the foam expands from the one side to the opposite side by 180 degrees because the foamed intermediate layer flow path (second passage 112) is a coat hanger tubular flow path. And it has the structure where the confluence | merging part where resin merges on the opposite side 180 degree | times arises. For this reason, uneven thickness of the foamed intermediate layer, insufficient foaming at the joining portion, and insufficient fusion occur, and as shown in FIG. 4, the thickness changes particularly at the joining portion on the opposite side of 180 degrees, flat cracking, etc. There was a drawback that it was likely to occur. In general, the resin tends to stay in the vicinity of the junction of the coat hanger tubular channel, and the vinyl chloride resin composition may be decomposed. In the figure, 120 is the outer layer and 121 is the inner layer. Reference numeral 122 denotes a foamed intermediate layer.

  In view of the above-mentioned drawbacks, the object of the present invention is to provide a three-layer foamed tube in which the vinyl chloride resin composition is less likely to stay or decompose in the resin passage, there is no uneven thickness or insufficient foaming of the foamed intermediate layer, and flat cracking does not occur easily. An object of the present invention is to provide a mold for a three-layer foamed tube that can be manufactured and a method for manufacturing a three-layer foamed tube using the same.

  The mold for a three-layer foamed pipe according to claim 1 is a cylindrical inner layer land / land that is substantially cylindrical, surrounds the core, and forms an annular first inner layer resin passage with a portion of the core. An intermediate layer resin passage that surrounds the intermediate layer core, the core and the inner layer land and intermediate layer core, and forms an annular intermediate layer resin passage between the core and the inner layer land and intermediate layer core. The land is formed by a spider having a through-hole, and the land is provided with a second inner layer resin passage opened in the annular outer layer resin passage and the intermediate layer resin passage. The resin passage for communication is connected to the upstream side of the first inner layer resin passage through the through hole of the spider, and the downstream side of the first inner layer resin passage and the outer layer resin passage is an abbreviation of the intermediate layer resin passage. Open at the same point, upstream of the intermediate layer resin passage On the upstream side of the outer layer resin passage and a second inner layer resin passage together with the first extruder is adapted to be connected, characterized in that the second extruder is adapted to be connected.

  Next, a description will be given with reference to the drawings. FIG. 1 is a cross-sectional view showing an example of a mold for a three-layer foamed pipe according to the present invention, and FIG. 2 is a cross-sectional view taken along line AA in FIG.

  In the figure, 1 is a substantially cylindrical core. Reference numeral 2 denotes a cylindrical inner layer land / intermediate core, which surrounds the core 1 and has an annular first inner layer resin passage 3 formed between the core 1 and a part thereof. The first inner layer resin passage 3 is a cross-head coat hanger type flow passage having an angle of 90 degrees between the resin injection direction and the mold outlet direction, and the resin supplied to the first inner layer resin passage 3 is It collides at a position of 180 degrees from the resin inlet and becomes a joint tube.

  In the figure, 4 is a land, which surrounds the core 1 and the inner layer land / intermediate layer core 2, and an annular intermediate layer resin passage 5 is formed between the core 1 and the inner layer land / intermediate layer core 2. ing. The torpedo 11 is connected to the upstream side of the core 1, the mold rear part 41 is connected to the upstream side of the land 4, and the intermediate layer resin passage 51 formed by the torpedo 11 and the mold rear part 41 is an intermediate layer resin. It communicates with the passage 5. A first extruder is connectable to the upstream side of the intermediate layer resin passage 51.

  The land 4 is formed with a second inner layer resin passage 31 that opens into the annular outer layer resin passage 6 and the intermediate layer resin passage 5. The outer layer resin passage 6 is a cross-head coat hanger type flow path having an angle of 90 degrees between the resin injection direction and the mold outlet direction, and the resin supplied to the first inner layer resin passage 3 is a resin injection port. It collides at a position of 180 degrees from and becomes a joint tube.

  The second inner layer resin passage 31 communicates with the upstream side of the first inner layer resin passage 3 through a through hole 71 formed in the spider 7 installed in the intermediate layer resin passage 5. . The spider 7 is a member that supports the core 1, and the shape thereof is not particularly limited, but it is preferable that the front end and the rear end are sharp so that the flow of the resin is not hindered, and the number thereof is also particularly Although not limited, generally, when extruding a pipe having an inner diameter of 50 mm, the number is four, and when extruding a pipe having an inner diameter of 100 mm, the number is eight. Further, it is not necessary to make a through hole in spiders other than the spider 7 that communicates the second inner layer resin passage 31 and the first inner layer resin passage 3.

  A second extruder 8 is connectable upstream of the outer layer resin passage 6 and the second inner layer resin passage 31.

  A die 9 surrounding the core portion 12 for the three-layer foam pipe, which is the downstream side of the core 1, is connected to the downstream side of the land 4, and a three-layer foam pipe passage 10 is formed between the die 9 and the core portion 12 for the three-layer pipe. Has been. The downstream side of the first inner layer resin passage 3 and the outer layer resin passage 6 is opened at substantially the same point from the inside and outside of the intermediate layer resin passage 5 in the vicinity of the connecting portion between the land 4 and the die 9.

  Therefore, each resin extruded through the first inner layer resin passage 3 and the outer layer resin passage 6 is laminated at the joining point on the foam layer extruded through the intermediate layer resin passage 5, and three-layer foaming is performed. A tube is obtained.

  The method for producing a three-layer foamed tube according to claim 3 uses the mold for a three-layer foamed tube according to claim 1 or 2 and uses a foamable vinyl chloride-based resin mainly composed of recycled vinyl chloride-based resin from the first extruder. A resin composition is supplied, and a vinyl chloride resin composition mainly comprising a virgin vinyl chloride resin is supplied from a second extruder and coextruded.

  The above recycled vinyl chloride resin refers to the scraps of vinyl chloride resin products collected from the city, scraps of molded products in the factory, and scraps generated at the start, stop or trouble of molding. This refers to a resin that is recycled, such as a crushed powder. These recycled resins may be used alone, but a virgin (unused) resin may be used in an arbitrary ratio in order to further improve molding stability.

  The foamable vinyl chloride resin composition is a composition mainly composed of recycled vinyl chloride resin and a foaming agent, and any known foaming agent can be used as the foaming agent. For example, azodicarbonamide, azobis Examples include pyrolytic foaming agents such as isobutyronitrile, physical foaming agents such as propane, pentane, hexane, and trichlorofluoromethane, and inert gases such as carbon dioxide and nitrogen.

  The virgin vinyl chloride resin is a resin obtained by polymerizing vinyl chloride monomer alone or a vinyl monomer having vinyl chloride as a main component, and the monomer having vinyl chloride as a main component is 50% by weight or more of chloride. It means a mixture of vinyl and a vinyl monomer copolymerizable therewith, and the copolymerizable monomer is a generally known vinyl monomer, such as vinyl acetate, alkyl (meth) acrylate, alkyl vinyl ether, ethylene, Examples thereof include vinyl fluoride and maleimide, and at least one of these can be used. The vinyl chloride resin used in the present invention may be a chlorinated vinyl chloride resin produced by chlorinating a vinyl chloride resin. The polymerization degree and chlorination degree of polyvinyl chloride in the vinyl chloride resin are not particularly limited.

  In the above recycled and virgin vinyl chloride resin composition, a stabilizer, a stabilizing aid, a lubricant, a processing aid, an impact modifier, and an antioxidant are added as necessary without departing from the object of the present invention. In addition, additives such as a light stabilizer, an ultraviolet absorber, a filler, a pigment, and a plasticizer may be added.

  The structure of the mold for a three-layer foamed pipe of the present invention is as described above, and the vinyl chloride resin composition is less likely to stay or decompose in the resin passage, and there is no uneven thickness of the foamed intermediate layer or insufficient foaming, and flat cracks are not caused. It is possible to produce a three-layer foam tube that is unlikely to occur.

  The structure of the manufacturing method of the three-layer foamed pipe of the present invention is as described above, and the three-layer foamed pipe is manufactured using the mold for the three-layer foamed pipe. Therefore, it is possible to produce a three-layer foamed tube that is less prone to flat cracking.

  Next, although an example of the present invention is given and explained, the present invention is not limited to the following example.

(Example 1)
The used vinyl chloride pipe for sewage (degree of polymerization 1050) was pulverized using a cutter mill, and then passed through a φ5 mm screen to obtain a recycled vinyl chloride resin pulverized product.
To 100 parts by weight of the obtained recycled vinyl chloride resin pulverized product, 2.0 parts by weight of lead-based heat stabilizer (manufactured by Shinagawa Chemical Co., Ltd., trade name: SAK-NS), polyethylene wax (manufactured by Mitsui Chemicals, trade name: Hiwax 220MP) 0.5 parts by weight, acrylic processing aid (manufactured by Mitsubishi Rayon Co., Ltd., trade name: Metabrene P-530A) 2.0 parts by weight, ester wax (manufactured by Cognis Japan, trade name: VPN 963) 0.7 Part by weight, 3.0 parts by weight of calcium carbonate (Shiraishi Kogyo Co., Ltd., trade name: Shiraka Hana CCR), 0.5 parts by weight of pigment and 0.5 parts by weight of azodicarbonamide are fed to a Henschel mixer and mixed to recycle vinyl chloride A resin composition was obtained.

  As a vinyl chloride resin composition for forming the inner and outer layers, a vinyl chloride resin for hard vinyl chloride pipes (trade name: TR1000R, polymerization degree 1050, manufactured by Tokuyama Sekisui Co., Ltd.) defined in JIS K 6741 was used.

  In performing extrusion molding, the mold shown in FIG. 1 includes a first extruder for intermediate layer, a second extruder for inner and outer layers, a cooling water tank in which tubes for tube outer surface molding are attached, a take-off machine, and a cutting machine. The manufacturing equipment connected to the machine was used.

  The vinyl chloride resin composition is supplied to the second extruder, kneaded at 190 ° C., injected into the mold at an extrusion rate of 60 kg / hr, and the recycled vinyl chloride resin composition is supplied to the first extruder at 190 ° C. The mixture was kneaded and injected into the mold at an extrusion rate of 90 kg / hr. The product outer diameter of the mold was 114 mm, and the inner diameter was about 100 mm. The resin tube discharged from the mold was inserted into the tube outer surface forming tube, cooled in a cooling water tank, taken up with a take-up machine, and then cut into a predetermined length with a cutting machine to obtain a three-layer foamed tube .

  Except that the mold shown in FIG. 3 was used, extrusion was performed using the same raw materials, the same extruder, and the same extrusion conditions as in Example 1 to obtain a three-layer foamed tube.

  The uneven thickness and expansion ratio of the foamed intermediate layer of the obtained three-layer foamed tube and the 5% flat strength of the three-layer foamed tube were measured. Further, the resin stayed in the mold after molding and the presence or absence of decomposition products were observed. The results are shown in Table 1.

In addition, the physical property measuring method was as follows.
(1) Uneven thickness of intermediate layer Extrusion was performed with the wall thickness at the mold outlet made uniform, and the uneven thickness of the intermediate layer of the resulting three-layer foamed tube was evaluated. The thickness of the intermediate layer of the three-layer foamed tube was measured, and the difference between the maximum value and the minimum value was measured.

(2) Foaming ratio The foaming ratio of the intermediate layer of the obtained three-layer foamed tube was determined from the following formula. The measurement was performed at 8 locations in the circumferential direction and indicated as an average value.
The specific gravity of the foam tube is calculated from the buoyancy generated when the foam is submerged in water.
Foaming ratio = specific gravity of a molded body obtained by extruding a compounding composition not containing a foaming agent / specific gravity of a foamed body

(3) 5% flat strength The obtained three-layer foamed tube is cut into a length of 200 mm, sandwiched between two flat plates, and the outer diameter of the tube at a speed of 10 mm / min in a direction perpendicular to the tube axis. The flat strength was calculated from the load at that time.

(4) Retention after molding, presence / absence of decomposition products After extrusion for 8 hours, the mold was disassembled, and the presence / absence of retention and decomposition products on the mold channel surface was visually confirmed.

It is sectional drawing which shows an example of the metal mold | die for three-layer foam pipes of this invention. It is AA sectional drawing in FIG. It is sectional drawing which shows an example of the conventional metal mold | die for three-layer foam pipes. It is sectional drawing which shows an example of the three-layer foam pipe manufactured with the conventional mold for three-layer foam pipes.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Core 2 Inner layer land and intermediate layer core 3 First inner layer resin passage 4 Land 5 Intermediate layer resin passage 6 Outer layer resin passage 7 Spider 8 Second extruder 9 Die 120 Outer layer 121 Inner layer 122 Foam intermediate layer

Claims (3)

  Cylindrical inner core land / intermediate layer core, core and inner land land / intermediate core, forming a substantially cylindrical core, surrounding the core, and forming an annular first inner layer resin passage between the core and a portion of the core Comprising a spider having a through-hole, which is disposed in a land and an intermediate layer resin passage which surrounds the core for use and which forms an annular intermediate layer resin passage between the core and the inner layer land / intermediate layer core, The land is provided with a second inner layer resin passage that opens to the annular outer layer resin passage and the intermediate layer resin passage, and the second inner layer resin passage passes through the through hole of the spider and is first. And the downstream side of the first inner layer resin passage and the outer layer resin passage open at substantially the same point of the intermediate layer resin passage, and the intermediate layer resin passage The first extruder can be connected to the upstream side of Three-layer foam tube mold, wherein the second extruder is adapted to be connected on the upstream side of the Rutotomoni outer layer resin passage and a second inner layer resin passage.   3. The first inner layer resin passage and the outer layer resin passage are cross-head coat hanger type flow paths having an angle of 90 degrees between the resin injection direction and the mold outlet direction. Mold for layered foam tube.   A foamable vinyl chloride resin composition mainly composed of recycled vinyl chloride resin is supplied from a first extruder using a mold for a three-layer foamed pipe according to claim 1 or 2, and a virgin is supplied from a second extruder. A method for producing a three-layer foamed tube, characterized in that a vinyl chloride resin composition mainly comprising a vinyl chloride resin is supplied and coextruded.

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